Sewing method and apparatus



April 4, 1967 c, CHEZAUD ET AL 3,312,185

SEWING METHOD AND APPARATUS Filed May 22, 1964 2 Sheets-Sheet 1 ear Q, ke I erre Burl/207 DOWvbzzgae/fidfif/er/ lnvenlors ttorneys April 4, 1967 J c. CHEZAUD ETAL 3,312,185-

SEWING METHOD AND APPARATUS Filed May 22, 1964 2 sham-sheet a Inventors J34?! C. C'bez add I /e 1- re 5a n l/w: 10027713 134 6 Max 8 5 r ZW Attorneys- 3 Claims. :1. 112-262) The present invention relates to a method for the sewing of flat elements, such as fabrics or sheets by means of sewing threads exhibiting a considerable degree of elasticity, for example synthetic filaments or threads. It also relates to apparatus for carrying the said process into effect.

When sewing together fabrics on a sewing machine, using mainly or wholly sewing threads or filaments having a considerable degree of elasticity, certain difficulties are encountered such as puckering. The sewing machines currently used have not been designed for use with these sewing threads or the like; they are generally equipped with tension devices which brake the sewing thread permanently so that, when an elastic synthetic sewing thread is used the latter is stretched and consequently returns resiliently when the sewing operation has been completed, so that puckering takes place.

In order to overcome this disadvantage, the tension of the sewing thread has been diminished as much as possible but the tension cannot fall below the value necessary for knotting or joining of the sewing stitch.

It is an object of the present invention to provide a sewing method and apparatus which overcome this difficulty.

According to one aspect of the present invention there is provided a method of sewing flat elements on a sewing machine having a needle carrying a sewing thread, said method comprising causing the needle to pierce the flat element and thereby to form a stitch, tensioning said thread only at the moment of forming the stitch and detensioning said thread for the remainder of the sewing.

According to a further aspect of the invention there is provided a sewing apparatus comprising a sewing machine having a needle reciprocable through an aperture in the needle plate of the machine and means for tensioning the sewing thread used with said needle only as the latter passes through the aperture in the needle plate.

In order that the invention may more readily be understood, the following description is given by way of example. Reference is made to the accompanying drawings, in which:

FIGURE 1 is a side elevation of one embodiment of sewing apparatus according to the invention;

FIGURE 2 is a top plan view of the tensioning member forming part of the apparatus;

FIGURE 3 is a fragmentary part elevation of the tensioning member shown in the inoperative position;

FIGURE 4 is a view similar to FIGURE 3 showing the tensioning member in the operative position; and

FIGURE 5 shows schematically the drive arrangement for the needle and tensioning member of the sewing apparatus of FIGURE 1.

The apparatus illustrated in FIGURE 1 shows, diagrammatically, a sewing machine in which the sewing thread 1 obtained from the reel 2 passes onto the thread guides 3 and 3' onto a tensioning member 4 and onto a thread take-up device 5 before reaching the needle 6. As seen in FIGURE 5 the needle is reciprocate/d by a crank 21 driven by shaft 22 which in turn is driven by a motor (not shown).

The tensioning member is illustrated in FIGURES 2,

States Patent 0 3 and 4. It consists of a cylinder 7 formed with a circular groove and mounted on a pivot on which it is free- 1y rotatable. A brake shoe 8 when applied to the periphery of the cylinder 7, effects the tensioning of the thread.

FIGURE 3 illustrates the brake shoe 8 mounted on a pivoting support 9 in its inoperative position spaced from cylinder 7. As can be seen in FIGURE 2, the brake shoe 8 is disposed axially spaced apart from the groove in the cylinder 7 in which the sewing thread 1 travels.

FIGURE 4 illustrates the brake shoe pivoted to the operative position where it is pressed against the periphery of cylinder 7. The means for moving the brake shoe is illustrated in FIGURE 5 and comprises a lever 24, reciprocat-ed by cam 23 on shaft 22, the lever being con-- nected to support 9 of the brake shoe. The movement of the brake shoe is thus synchronised with that of the needle.

In use of the apparatus of this invention the sewing thread I1 coming from the reel 2 passes into the groove in the cylinder 7, in which it describes an arc or possibly one or more complete revolutions, and then passes to the thread stretcher 5. The cylinder 7 is freely mounted so that it does not impart any permanent tension to the sewing thread I. At the instant of kn-otting the stitch, the shoe 8 is applied on the cylinder 7 by the means shown in FIGURE 5 which is connected to the arrangement providing for the ascending and descending movement of the needle. The device may alternatively be connected to the arrangement for raising and lowering the feed dogs. The sewing thread is then braked and has the necessary tension for knotting the stitch. The shoe 8 then comes away from the grooved cylinder 7 between the formation of two stitches.

A variant of the device described hereinabove could consist in utilizing a braking device operating intermittently by magnetic effect or electro-magnetic effect, the device being synchronised with the formation of the stitch.

The process and the apparatus according to the invention are obviously suitable for the sewing of knitted, woven or nonwoven fabrics or sheets, whatevertheir nature, is. whether synthetic, artificial or natural. They are more particularly suitable for sewing with the aid of sewing yarns or threads exhibiting a considerable degree of elasticity, such as artificial and synthetic filaments and threads, silk threads, wool threads, texturised threads or special threads, but they can also be used with advantage for sewing with sewing threads of slight elasticity such as cotton, flax, hemp, jute, ramie or China grass, etc., so that it is possible to utilize the same machine for various uses.

Mention has been made of a single needle and a single sewing thread. It is quite clear that it would be possible to use the device described hereinabove on a sewing machine equipped with a multiplicity of needles, without thereby exceeding the scope of the present invention.

We claim:

1. A method of sewing flat elements on a sewing machine having a needle carrying a sewing thread, such method comprising the steps of causing the needle to pierce the flat element and thereby to form a stitch, tensioning said thread only at the moment of tightening of the stitch and completely detensioning said thread for the remainder of said sewing.

2. A sewing apparatus comprising a sewing machine having a needle adapted to hold a sewing thread; a needle plate; means defining an aperture in said needle plate below said needle; crank means for reciprocating said needle through said aperture; a freely rotatable roller around which said sewing thread may be passed; a brake shoe positioned adjacent said roller and cam means operatively connected to said crank means for applying said shoe against said roller to arrest the latter thereby to tension said thread only when said needle is passing through said aperture.

3. A sewing apparatus comprising a sewing machine having a needle adapted to hold a sewing thread; a needle plate; means defining an aperture in said needle plate below said needle; means for reciprocating the needle through said aperture; a reel for said thread; a freely rotatable roller around which said sewing thread may be passed, positioned between said reel and needle; a brake shoe positioned adjacent said roller and means for applying said shoe against said roller to arrest the latter and thereby tension said sewing thread only when said needle is passing through said aperture.

References Cited by the Examiner UNITED STATES PATENTS 0 PATRICK D. LAWSON, Primary Examiner.

RICHARD I SCANLAN, JR., Examiner. 

1. A METHOD OF SEWING FLAT ELEMENTS ON A SEWING MACHINE HAVING A NEEDLE CARRYING A SEWING THREAD, SUCH METHOD COMPRISING THE STEPS OF CAUSING THE NEEDLE TO PIERCE THE FLAT ELEMENT AND THEREBY TO FORM A STITCH, TENSIONING SAID THREAD ONLY AT THE MOMENT OF TIGHTENING OF THE STITCH AND COMPLETELY DETENSIONING SAID THREAD FOR THE REMAINDER OF SAID SEWING. 